Jupiter

Voyager 1 took this photo of Jupiter on February 1, 1979, while 32.7 million kilometres from the planet. Visible are the coloured cloud bands and the Great Red Spot. The moon Io can also be seen at the upper right.Source: Courtesy NASA/JPL-Caltech

Average Distance from the Sun:778.34 million km (5.202 AU)

Size (Equatorial Diameter):142 200 km (11.14 x that of Earth)

Mass:1.899 x 1027 kg (317.89 x that of Earth)

Length of Day (Solar Rotation Period):9.83 Earth hours

Length of Year (Sidereal Orbital Period):11.86 Earth years

Temperature:-150° C (clouds)

Gravity:22.88 m/s2 (2.33 x that of Earth)

Jupiter is the largest planet in our Solar System, a thousand times the size of the Earth in volume, and the first of the Gas Giants. It is the second brightest planet in our night sky and has been known since ancient times.

Another photograph of Jupiter taken by the Voyager 1 spacecraft, showing the Great Red Spot and the moons Io (left) and Europa.Source: Courtesy NASA/JPL-Caltech.

Jupiter is the largest planet in our Solar System, a thousand times the size of the Earth in volume, and the first of the Gas Giants. It is the second brightest planet in our night sky and has been known since ancient times.

Surface and Atmosphere

Jupiter is mostly made of gases so there is no solid surface.

The outer layers of Jupiter are mostly formed of the gases hydrogen and helium but there are small amounts of water droplets, ice crystals, ammonia crystals and other elements. Clouds of these elements form in the hydrogen these clouds can be white, shades of orange, brown and red. The gases swirl around in huge storms as well as rotating about the planet very quickly.

One of Jupiter's most famous features is the Great Red Spot, which was first recorded by Cassini in 1665. This is an enormous storm, up to 40,000 km long by 14,000 km wide.

Deep inside the planet, the gases become very thick, so thick they are almost like a liquid. Deeper still there may be a layer like liquid metal and at the very centre Jupiter may have a small solid core. Towards the core it gets hotter, the liquid-like level probably being about 11,000°C and the core about 30 000°C.

Moons

Jupiter has a total of 40 moons consisting of 4 large moons, 23 smaller moons and 13 even smaller moons that were discovered recently but are as yet unnamed.

These are known as the Galilean satellites, named after Galileo Galilei, who discovered them in 1610. They were the first moons found around another planet.

Ganymede is the largest moon in the Solar System, larger even than the planets Mercury and Pluto. Its composition is half water or ice and half rock.

Callisto is slightly smaller and has a lower density, suggesting large amounts of water, and has the most cratered surface of any object yet found in the solar system.

Io has a strange orange and yellow coloured surface, caused by volcanoes bringing sulfurous material to the surface. These were the first active volcanoes found on a world other than the Earth when they were discovered by the Voyager spacecraft.

Europa is the brightest of the Galilean satellites and appears to have an ocean of liquid water, covered by a thin ice crust. The crust is covered in cracks and streaks, indicating that it has been fractured. It has, however, the smoothest surface of any moon in the solar system.

Of Jupiter's smaller moons, four are found inside the orbit of Io. Three of these inner moons were discovered by Voyager 1 (1979) while a fourth was found by direct observation in 1982. Eight of Jupiter's outer moons were discovered prior to 1974. In 1999 and 2000, 24 new moons of Jupiter were discovered, 11 of these were assigned names by the International Astronomical Union in 2002.

Rings

Jupiter’s rings were first discovered by Voyager 1 in 1979. Voyager 1 & 2 revealed a flattened main ring, an inner ring (halo ring) and a third, fainter outer ring (gossamer ring). Galileo found the gossamer ring consisted of two rings and one is embedded within the other, and both are composed of microscopic debris from two small moons, Amalthea and Thebe. The rings start at 20 500 km from Jupiter’s cloud tops and extend out to 250 000 km.

In Mythology

Jupiter was the principal Roman god, originally the god of the sky. He is identified with the Greek god Zeus, a weather god responsible for rain, hail, snow and particularly thunder and lightning.

Hi there - Jupiter has 3 or 4 rings, depending on if you count the outer "gossamer" layer as one or two rings! If you would like more pictures of Jupiter, check out the Hubble site's gallery of Jupiter images.